Semiconductor device and manufacturing method of semiconductor device

ABSTRACT

According to one embodiment, a semiconductor substrate, a metal film, a surface modifying layer, and a redistribution trace are provided. On the semiconductor substrate, a wire and a pad electrode are formed. The metal film is formed over the semiconductor substrate. The surface modifying layer is formed on a surface layer of the metal film and improves the adhesion with a resist pattern. The redistribution trace is formed on the metal film via the surface modifying layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2010-198379, filed on Sep. 3, 2010 and the prior Japanese Patent Application No. 2010-212184, filed on Sep. 22, 2010; the entire contents all of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to a semiconductor device and a manufacturing method of a semiconductor device.

BACKGROUND

In order to achieve high integration and high performance of semiconductor devices, improvement of an operation speed and increase in capacity of memories are required. Accordingly, fine redistribution traces with a pitch of 10 um or less are required also in a redistribution trace forming process on a semiconductor substrate.

If the pitch of redistribution traces is reduced, the adhesion between a resist pattern for patterning a redistribution trace and a base thereunder decreases, which results in causing resist stripping in some cases at the time of resist development or the like.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A to FIG. 1E are cross-sectional views illustrating a manufacturing method of a semiconductor device according to a first embodiment;

FIG. 2A to FIG. 2D are cross-sectional views illustrating the manufacturing method of the semiconductor device according to the first embodiment;

FIG. 3A to FIG. 3C are cross-sectional views illustrating the manufacturing method of the semiconductor device according to the first embodiment;

FIG. 4A and FIG. 4B are cross-sectional views illustrating the manufacturing method of the semiconductor device according to the first embodiment;

FIG. 5A and FIG. 5B are cross-sectional views illustrating the manufacturing method of the semiconductor device according to the first embodiment;

FIG. 6A and FIG. 6B are cross-sectional views illustrating the manufacturing method of the semiconductor device according to the first embodiment;

FIG. 7 is a diagram illustrating a relationship between exposure doses on a surface and a lower surface of resists A and B having different absorbance according to the first embodiment;

FIG. 8A to FIG. 8E are cross-sectional views illustrating a manufacturing method of a semiconductor device according to a third embodiment;

FIG. 9A to FIG. 9D are cross-sectional views illustrating the manufacturing method of the semiconductor device according to the third embodiment;

FIG. 10A to FIG. 100 are cross-sectional views illustrating the manufacturing method of the semiconductor device according to the third embodiment;

FIG. 11A and FIG. 11B are cross-sectional views illustrating the manufacturing method of the semiconductor device according to the third embodiment;

FIG. 12A and FIG. 12B are cross-sectional views illustrating the manufacturing method of the semiconductor device according to the third embodiment; and

FIG. 13A and FIG. 13B are cross-sectional views illustrating the manufacturing method of the semiconductor device according to the third embodiment.

DETAILED DESCRIPTION

In general, according to one embodiment, a semiconductor substrate, a metal film, a surface modifying layer, and a redistribution trace are provided. On the semiconductor substrate, a wire and a pad electrode are formed. The metal film is formed over the semiconductor substrate. The surface modifying layer is formed on a surface layer of the metal film and improves the adhesion with a resist pattern. The redistribution trace is formed on the metal film via the surface modifying layer.

A semiconductor device and a manufacturing method of a semiconductor device according to the embodiments will be explained below with reference to the drawings. The present invention is not limited to these embodiments.

First Embodiment

FIG. 1A to FIG. 1E, FIG. 2A to FIG. 2D, FIG. 3A to FIG. 3C, FIG. 4A and FIG. 4B, FIG. 5A and FIG. 5B, and FIG. 6A and FIG. 6B are cross-sectional views illustrating a manufacturing method of a semiconductor device according to the first embodiment.

In FIG. 1A, on a base material layer 1, a pad electrode 2 a and a wire 2 b are formed and a protective film 3 is formed to cover the pad electrode 2 a and the wire 2 b. Moreover, in the protective film 3, an opening 3 a that exposes the pad electrode 2 a and an opening 3 b that exposes part of the wire 2 b are formed.

As the base material layer 1, for example, a semiconductor substrate on which an integrated circuit, such as a logic circuit or a DRAM, is formed can be used. Moreover, as the material of the pad electrode 2 a and the wire 2 b, for example, Al or Al-based metal can be used. Furthermore, as the material of the protective film 3, for example, an insulator, such as a silicon oxide film, a silicon oxynitride film, or a silicon nitride film, can be used.

Next, as shown in FIG. 1B, a buffer layer 4 is formed on the protective film 3 by applying photosensitive resin or the like to the protective film 3. As the material of the buffer layer 4, for example, polyimide resin can be used. For reducing wafer stress, it is applicable to use acrylic resin or phenolic resin whose curing temperature is lower than polyimide resin.

Next, as shown in FIG. 1C, openings 4 a and 4 b, which expose the pad electrode 2 a and part of the wire 2 b, respectively, are formed in the buffer layer 4 by using the photolithography technology.

Next, as shown in FIG. 1D, a metal film 5 is formed on the pad electrode 2 a, the wire 2 b, the protective film 3, and the buffer layer 4 by using a method such as sputtering, plating, CVD, ALD, or vapor deposition. As the metal film 5, an under barrier metal film can be used, and, for example, a stacked structure of Ti and Cu stacked thereon can be used. It is applicable to use a material such as TiN, TiW, W, Ta, Cr, Co, or CoTi instead of Ti. Moreover, it is applicable to use a material such as Al, Pd, Au, or Ag instead of Cu.

Next, as shown in FIG. 1E, a resist film 6 is formed on the metal film 5 by using a method such as spin coating. The resist film 6 is such that the absorbance is set to 80% or less with respect to light that reaches the interface (hereinafter, base interface) with the metal film 5. The absorbance in the present invention is a value measured by using an exposure apparatus with i-line wavelength (365 nm). The film thickness of the resist film 6 can be set within a range of 1 to 50 μm.

Next, as shown in FIG. 2A, openings 6 a to 6 c are formed in the resist film 6 by performing exposure and development on the resist film 6. The opening 6 a can be arranged over the pad electrode 2 a, the opening 6 b can be arranged over the buffer layer 4, and the opening 6 c can be arranged over the wire 2 b. The width of the resist film 6 in which the opening 6 b is formed can be 20 μm or less.

Next, as shown in FIG. 2B, redistribution traces 7 a to 7 c are formed on the pad electrode 2 a, the buffer layer 4, and the wire 2 b, respectively, via the metal film 5 by embedding a first conductor in the openings 6 a to 6 c by electroplating. Moreover, surface layers 8 a to 8 c are formed on the redistribution traces 7 a to 7 c, respectively, by embedding a second conductor in the openings 6 a to 6 c by electroplating. The redistribution trace 7 a can be used for connection with the pad electrode 2 a. The redistribution trace 7 c can be used for connection with the wire 2 b. The redistribution trace 7 b can be used, for example, for routing the redistribution trace 7 a and 7 c on the buffer layer 4.

For the surface layers 8 a to 8 c, a material having a higher etch resistance than the redistribution traces 7 a to 7 c can be used. For example, the material of the redistribution traces 7 a to 7 c can be Cu or Cu-based metal, and the material of the surface layers 8 a to 8 c can be selected from at least any one of Ni, Mn, Ta, Zn, Cr, Co, Sn, and Pb. Moreover, desirably, the width of the redistribution trace 7 b is 20 μm or less and the half pitch of the redistribution trace 7 b is 40 μm or less.

Next, as shown in FIG. 2C, the resist film 6 on the metal film 5 is removed by a method such as ashing.

The absorbance of the resist film 6 is set to 80% or less with respect to light having a wavelength of 365 nm, so that the degree of crosslinking at the base interface of the resist film 6 can be increased while suppressing increase in the degree of crosslinking on the surface of the resist film 6 at the time of exposure of the resist film 6. Therefore, the adhesion with the base interface of the resist film 6 can be improved while suppressing excessive curing of the surface of the resist film 6, so that even when the width of the resist film 6 in which the opening 6 b is formed is small, the resist film 6 can be suppressed from stripping at the time of development and moreover, even when there is a wide resist film 6 in other areas, the resist film 6 can be removed after forming the redistribution traces 7 a to 7 c.

If the remaining width of the resist film 6 is 20 μm or less, stripping becomes severe significantly, so that the remaining width is preferably 20 μm or less. The half pitch is preferably 40 μm or less.

Next, as shown in FIG. 2D, the metal film 5 is etched with the redistribution traces 7 a to 7 c as a mask, thereby removing the metal film 5 around the redistribution traces 7 a to 7 c.

Next, as shown in FIG. 3A, a buffer layer 9 is formed on the wire 2 b, the buffer layer 4, and the surface layers 8 a to 8 c by applying photosensitive resin or the like to the wire 2 b, the buffer layer 4, and the surface layers 8 a to 8 c. As the material of the buffer layer 9, for example, polyimide resin can be used. For reducing wafer stress, it is applicable to use acrylic resin or phenolic resin whose curing temperature is lower than polyimide resin.

Next, as shown in FIG. 3B, openings 9 a and 9 b, which expose the surface layer 8 a over the pad electrode 2 a and part of the wire 2 b, respectively, are formed in the buffer layer 9 by using the photolithography technology.

Next, as shown in FIG. 3C, a metal film 10 is formed on the wire 2 b, the protective film 3, the buffer layers 4 and 9, and the surface layer 8 a by using a method such as sputtering, plating, CVD, ALD, or vapor deposition. As the metal film 10, for example, a stacked structure of Ti and Cu stacked thereon can be used.

Next, as shown in FIG. 4A, a resist film 11 is formed on the metal film 10 by using a method such as spin coating.

Next, as shown in FIG. 4B, an opening 11 a, which exposes the surface layer 8 a over the pad electrode 2 a, is formed in the resist film 11 by performing exposure and development on the resist film 11.

Next, as shown in FIG. 5A, a bump electrode is formed on the surface layer 8 a via the metal film 10 by sequentially embedding a barrier layer 12 and solder layers 13 and 14 in the opening 11 a by electroplating. For example, Ni can be used for the material of the barrier layer 12, Cu can be used for the material of the solder layer 13, and Sn can be used for the material of the solder layer 14.

Next, as shown in FIG. 5B, the resist film 11 on the metal film 10 is removed by a method such as ashing.

Next, as shown in FIG. 6A, the metal film 10 is etched with the bump electrode formed of the barrier layer 12 and the solder layers 13 and 14 as a mask, thereby removing the metal film 10 around the bump electrode formed of the barrier layer 12 and the solder layers 13 and 14.

Next, as shown in FIG. 6B, the solder layers 13 and 14 are reflowed, so that the solder layers 13 and 14 are alloyed to form an alloy solder layer 15 on the barrier layer 12.

The above processes can be performed in a state where the base material layer 1 is a wafer. Then, after the above processes, semiconductor chips can be cut out by singulating this wafer.

In the above embodiment, the method of using a solder ball as the bump electrode is explained, however, a nickel bump, a gold bump, a copper bump, or the like can be used instead. Moreover, in the above embodiment, explanation is given for the method of using a stacked structure of Ti and Cu as the metal films 5 and 10, however, Ti or Cu can be used alone, Cr, Pt, W, or the like can be used alone, or a stacked structure of these metals can be used.

Furthermore, as a joining method of the bump electrode, metal joint, such as solder joint and alloy joint, can be used, or ACF (Anisotropic Conductive Film) bonding, NCF (Nonconductive Film) bonding, ACP (Anisotropic Conductive Paste) bonding, NCP (Nonconductive Paste) bonding, or the like can be used.

FIG. 7 is a diagram illustrating a relationship between exposure doses on a surface and a lower surface of resists A and B having different absorbance according to the first embodiment. The absorbance of the resist A is set to 81% and the absorbance of the resist B is set to 42% with respect to light having a wavelength of 365 nm. Moreover, the film thickness of the resists A and B is set to 10 μm. Furthermore, a Cu film is used as the base underlying the resists A and B.

In FIG. 7, the exposure dose at the interface with the base decreases in the resist A compared with the resist B even if the exposure dose is the same on the surfaces. Therefore, in the resist A, if the exposure dose at the interface with the base is increased for improving the adhesion with the base, overexposure occurs on the surface, so that excessive curing of the surface occurs.

On the other hand, in the resist B, the exposure dose at the interface with the base can be increased without increasing the exposure dose on the surface, so that the adhesion with the base can be improved while preventing overexposure on the surface.

Next, a half pitch pattern of line & space of 3/3 μm to 15/15 μm is formed, and the relationship between the surface exposure dose of the resists A and B having different absorbance according to the first embodiment and the resist remaining width with which stripping occurs is checked.

As a result, it is found that, for example, for forming a resist pattern having a width of 5 μm without stripping, in the resist A, the exposure dose of 600 mJ/cm² or more is needed on the surface and therefore excessive curing of the surface occurs, so that the removability of the resist pattern decreases.

On the other hand, in the resist B, for forming a resist pattern having a width of 5 μm without stripping, the exposure dose of about 400 mJ/cm² on the surface is sufficient and therefore excessive curing of the surface can be prevented, so that decrease in removability of the resist pattern can be prevented.

Moreover, the relationship between the lower-surface exposure dose of the resists A and B having different absorbance according to the first embodiment and the resist remaining width with which stripping occurs is checked. For example, for forming a resist pattern having a width of 5 μm without stripping, in the resist A, the exposure dose of about 120 mJ/cm² is needed at the interface with the base. For obtaining the exposure dose of about 120 mJ/cm² at the interface with the base, the exposure dose of about 600 mJ/cm² is needed on the surface referring to FIG. 7 and therefore excessive curing of the surface occurs, so that the removability of the resist pattern decreases. In other words, it is found that because the absorbance exceeds 80% with respect to light having a wavelength of 365 nm in the resist A, the effect of the present invention cannot be obtained.

On the other hand, in the resist B, for forming a resist pattern having a width of 5 μm with without stripping, the exposure dose of about 200 mJ/cm² is needed at the interface with the base. For obtaining the exposure dose of about 200 mJ/cm² at the interface with the base, the exposure dose of about 400 mJ/cm² is sufficient on the surface referring to FIG. 7 and therefore excessive curing of the surface can be prevented, so that decrease in removability of the resist pattern can be prevented. In other words, it is found that, in the resist B in which the absorbance is 42% with respect to light having a wavelength of 365 nm, the effect of the present invention can be obtained. Therefore, the absorbance of the resist film 6 in the present invention is set to 80% or less, preferably 60% or less, and more preferably 50% or less with respect to light having a wavelength of 365 nm.

In the resist A, when the exposure dose is 400 mJ/cm², stripping does not occur in the case where the line & space is 10 μm or more. Moreover, in the resist A, when the exposure dose is 600 mJ/cm², stripping does not occur in the case where the line & space is 6 μm or more.

On the other hand, in the resist B, when the exposure dose is 400 mJ/cm², stripping does not occur in the case where the line & space is 5 μm or more. Moreover, in the resist B, when the exposure dose is 600 mJ/cm², stripping does not occur in the case where the line & space is 3 μm or more.

Second Embodiment

In the above first embodiment, explanation is given for the method of setting the absorbance of the resist film 6 to 80% or less with respect to light having the wavelength of 365 nm for preventing stripping of a resist pattern, however, it is applicable to reduce the solubility of the resist film 6 at the time of development to 1 μm/min or less. As the method of reducing the solubility of the resist film 6 at the time of development, it is possible to reduce alkali-soluble groups of the resist material.

Developer can be suppressed from penetrating the interface between the resist film 6 and the base by reducing the solubility of the resist film 6 at the time of development, so that stripping of a resist pattern can be reduced.

The relationship between the development time of resists C and D having different solubility according to the second embodiment and the resist remaining film thickness is checked. The conditions are as follows. Negative resist is used as the resists C and D, resist in which alkali-soluble groups are reduced by about 30% with respect to the resist C is used as the resist D, the film thickness of the resists C and D is set to 10 μm, and an Si substrate is used for the base.

As a result, whereas the development rate of the resist D is 2 μm/min, the development rate of the resist C is 0.67 μm/min. When this resist C is used, stripping of a resist pattern can be reduced compared with the case of using the resist D.

Third Embodiment

FIG. 8A to FIG. 8E, FIG. 9A to FIG. 9D, FIG. 10A to FIG. 10C, FIG. 11A and FIG. 11B, FIG. 12A and FIG. 12B, and FIG. 13A and FIG. 13B are cross-sectional views illustrating a manufacturing method of a semiconductor device according to the third embodiment.

In this third embodiment, in the process of FIG. 8E, a surface modifying layer 16 that improves the adhesion with the resist film 6 is formed on the metal film 5 before forming the resist film 6 on the metal film 5.

When the surface of the metal film 5 is Cu, a Cu oxide film can be used as the surface modifying layer 16. As the Cu oxide film, CuO is preferable and Cu₂O is more preferable. It is sufficient that the surface modifying layer 16 is present on the metal film 5 and the film thickness of the surface modifying layer 16 can be as small as about a few nm.

When a Cu oxide film is used as the surface modifying layer 16, the surface of Cu can be terminated with O, enabling to improve the adhesion with the resist film 6.

The method of forming the Cu oxide film on a Cu film includes a method of performing a heat treatment in an oxidizing atmosphere. The room temperature or higher is sufficient for the temperature in this heat treatment. However, for shortening the formation time of the Cu oxide film, the temperature in the heat treatment is preferably set to a few hundred degrees Celsius or higher.

In FIG. 8A to FIG. 8E, FIG. 9A to FIG. 9D, FIG. 10A to FIG. 10C, FIG. 11A and FIG. 11B, FIG. 12A and FIG. 12B, and FIG. 13A and FIG. 13B, the processes similar to FIG. 1A to FIG. 1E, FIG. 2A to FIG. 2D, FIG. 3A to FIG. 3C, FIG. 4A and FIG. 4B, FIG. 5A and FIG. 5B, and FIG. 6A and FIG. 6B can be performed except for the method of forming the surface modifying layer 16 on the metal film 5 in the process in FIG. 8E.

The resist remaining width with which stripping occurs in the case of different base surface states according to the third embodiment is checked with the surface exposure dose of 300 mJ/cm². When a resist pattern is directly formed on the Cu film, the strip-resistant resist remaining width is about 6 μm. On the other hand, when a resist pattern is formed after forming the Cu oxide film as the surface modifying layer on the Cu film by a heat treatment, the strip-resistant resist remaining width is about 3 μm. Therefore, it is found that resist stripping can be suppressed by providing the surface modifying layer.

As this resist pattern, a half pitch pattern of line & space of 3/3 μm to 15/15 μm is used.

While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions. 

What is claimed is:
 1. A semiconductor device comprising: a semiconductor substrate on which a wire and a pad electrode are formed; a metal film formed over the semiconductor substrate; a surface modifying layer formed on a surface layer of the metal film; and a redistribution trace formed on the metal film via the surface modifying layer.
 2. The semiconductor device according to claim 1, wherein the metal film has a stacked structure in which a lower layer is selected from any of Ti, TiN, TiW, W, Ta, Cr, and CoTi and an upper layer is a selected from any of Cu, Al, Pd, Au, and Ag, and the surface modifying layer is a Cu oxide film.
 3. The semiconductor device according to claim 1, further comprising a surface layer formed on the redistribution trace.
 4. The semiconductor device according to claim 3, wherein a material of the redistribution trace is Cu and a material of the surface layer is selected from at least any one of Mn, Ta, Ni, Zn, Cr, Co, Sn and Pb.
 5. The semiconductor device according to claim 1, wherein an integrated circuit is formed on the semiconductor substrate.
 6. The semiconductor device according to claim 1, further comprising: a protective film formed on the semiconductor substrate to cover the wire and the pad electrode; a first opening that is formed in the protective film and exposes the pad electrode; and a second opening that is formed in the protective film and exposes part of the wire.
 7. The semiconductor device according to claim 6, further comprising: a first buffer layer formed on the protective film; a third opening that is formed in the first buffer layer and exposes the pad electrode through the first opening; and a fourth opening that is formed in the first buffer layer and exposes part of the wire through the second opening.
 8. The semiconductor device according to claim 7, wherein the protective film is an inorganic insulator and the first buffer layer is resin.
 9. The semiconductor device according to claim 8, wherein the resin is selected from polyimide resin, acrylic resin, and phenolic resin.
 10. The semiconductor device according to claim 9, wherein the metal film includes a first under barrier metal film formed between the first buffer layer and the redistribution trace.
 11. The semiconductor device according to claim 10, wherein the redistribution trace includes a first redistribution trace connected to the pad electrode through the first opening and the third opening, a second redistribution trace connected to the wire through the second opening and the fourth opening, and a third redistribution trace formed over the first buffer layer.
 12. The semiconductor device according to claim 11, further comprising: a second buffer layer formed over the first redistribution trace, the second redistribution trace, and the third redistribution trace; and a fifth opening that is formed in the second buffer layer and exposes the first redistribution trace.
 13. The semiconductor device according to claim 12, further comprising a bump electrode connected to the first redistribution trace through the fifth opening.
 14. The semiconductor device according to claim 13, wherein the bump electrode is formed of an alloy solder layer.
 15. The semiconductor device according to claim 14, wherein the metal film includes a second under barrier metal film formed between the second buffer layer and the bump electrode.
 16. The semiconductor device according to claim 15, wherein the second buffer layer is resin.
 17. The semiconductor device according to claim 16, wherein the resin is selected from polyimide resin, acrylic resin, and phenolic resin.
 18. A manufacturing method of a semiconductor device comprising: forming a metal film over a semiconductor substrate on which a wire and a pad electrode are formed; forming resist patterns, whose absorbance with respect to light having a wavelength of 365 nm that reaches an interface with the metal film is 80% or less, on the metal film; forming a redistribution trace embedded between the resist patterns on the metal film; and removing the resist patterns from the metal film after forming the redistribution trace.
 19. A manufacturing method of a semiconductor device comprising: forming a metal film over a semiconductor substrate on which a wire and a pad electrode are formed; forming resist patterns, whose solubility at a time of development is 1 μm/min or less, on the metal film; forming a redistribution trace embedded between the resist patterns on the metal film; and removing the resist patterns from the metal film after forming the redistribution trace.
 20. A manufacturing method of a semiconductor device comprising: forming a metal film over a semiconductor substrate on which a wire and a pad electrode are formed; forming a surface modifying layer on a surface layer of the metal film; forming resist patterns over the metal film; forming a redistribution trace embedded between the resist patterns over the metal film; and removing the resist patterns from the metal film after forming the redistribution trace. 